University of Illinois

No. 7/May 9, 1997

Black Cutworm Moth Migratory Update and Projected Cutting Dates

Black cutworm moths continued to be caught in cooperators' pheromone traps throughout the state for the monitoring period of April 26 to May 2. Moths were captured as far south as Pope County and northward to Boone, McHenry, and Stephenson counties. The west to east distribution of moth captures was equally wide with moths caught from Adams County to Vermilion County. So far, black cutworm moth captures this spring can best be characterized as very widely scattered, with only occasional intense flights (nine or more moths caught over a 1- to 2-day period). Intense flights for the most recent monitoring period were recorded in Adams (4/29), Ford (4/28), and Pike (4/26) counties. In all, moth captures occurred in 31 counties throughout Illinois. Bob Scott, Illinois State Water Survey, has provided projected cutting dates for these most recent intense flights: Adams (5/22), Ford (5/26), and Pike (5/21). Please refer to previous issues of this Bulletin for projected cutting dates based upon intense flights that occurred earlier this spring.

Observations of very weedy fields across a wide area of southern Illinois suggest that growers in this region of the state should remain extra vigilant in their management of black cutworms. When you are monitoring fields for suspected cutworm injury, we suggest examining 250 plants (50 plants in each of five locations) in a field. Pay particular attention to areas with a great deal of plant residue or low areas with poor drainage. When injured plants are found, dig around the bases of the plants to look for live cutworm larvae. Collect at least 10 larvae and determine their age by using the head-capsule gauge shown in Figure 1. Fourth instars will feed for about 25 more days and may consume as many as four corn plants in the one-leaf stage. On the other hand, seventh instars are almost done feeding and should pupate soon. A large number of fourth and fifth instars is more threatening than a large number of seventh instars. Please let us know if you begin to find economic infestations of black cutworms, and we will report these observations to our readers.

Mike Gray, and Kevin Steffey, Extension Entomology, (217)3336652